codemod(turbopack): Replace `return Err(anyhow!())` with `anyhow::bail!()` (#72487)
Early returns should use `anyhow::bail!()`.
Ran ast-grep with
```bash
sg run --lang rust --pattern 'return Err(anyhow!($$$ARGS));' --rewrite 'anyhow::bail!($$$ARGS)' --update-all && sg run --lang rust --pattern 'return Err(anyhow::anyhow!($$$ARGS));' --rewrite 'anyhow::bail!($$$ARGS)' --update-all && cargo fmt
```
Manually cleaned up unused import warnings (second commit) because `cargo fix` hangs (idle, no CPU usage) about halfway through our build, and I'm not sure why. I tested the latest nightly, and it hangs too.